Field of Invention
The present invention relates to a lock-up device, particularly to a lock-up device for a torque converter, which is disposed between a front cover coupled to an engine-side member and a turbine hub coupled to a transmission.
Background Information
A torque converter is equipped with a lock-up device to reduce fuel consumption. The lock-up device is disposed in a space produced between a front cover and a turbine, and is configured to mechanically couple the front cover and the turbine to directly transmit a torque therebetween.
In general, the lock-up device includes a piston, to which a friction member is mounted as a clutch portion, and a damper mechanism. The piston is pressed onto the front cover by the action of hydraulic pressure and a torque is transmitted to the piston from the front cover through the friction member. The damper mechanism includes an output-side member coupled to the turbine and a plurality of torsion springs for elastically coupling the piston and the output-side member. Furthermore, the torque transmitted to the piston is transmitted to the output-side member through the plural torsion springs, and is further transmitted to the turbine.
Incidentally, Japanese Laid-open Patent Application Publication No. 2012-87856 describes a lock-up device including a dynamic damper mechanism in which an inertia member is mounted to the output-side member to inhibit variation in engine rotation. In the lock-up device, the inertia member is mounted to the output member fixed to the turbine to be rotatable relative thereto. Furthermore, torsion springs are mounted as elastic members between the output member and the inertia member.
Moreover, in the device of Japanese Laid-open Patent Application Publication No. 2012-87856, a hysteresis torque generating mechanism is mounted between the output member and the inertia member. The hysteresis torque generating mechanism is configured to make the magnitude of hysteresis torque vary depending on rotational speed ranges, and thereby, reduce variation in output-side rotational speed over wide rotational speed ranges.